A BMW M car that sees sustained track use asks more of its brakes than a single hard stop. The Pro-System G8x package brings Alcon GT3 calipers together with 390mm front and 355mm rear discs in a complete front-and-rear system. The focus is the complete braking assembly: caliper support, friction capacity, rotor cooling and a practical route to servicing the components that wear.

Alcon / Pro-System BMW G8x GT3 Brake System

BRK.200645 identifies the complete-car package listed for BMW G8x M2, M3 and M4 applications. Its GT3 caliper configuration is a distinct system specification. The front and rear components should be selected and serviced as that package, with friction material and wheel clearance considered alongside the mechanical hardware.

Features

• Alcon GT3 caliper configuration
• 390mm front disc diameter
• 355mm rear disc diameter
• Front-and-rear package under one vendor part number: BRK.200645
• Pro-System floating rotor architecture with separately serviceable friction rings
• Application-specific hats, brackets and mounting interfaces

Alcon GT3 Calipers

The caliper supports the pads and turns hydraulic pressure into clamping force. Its stiffness, mounting and pad support matter when the system is repeatedly loaded at high temperature. This package uses Alcon’s GT3 caliper configuration, rather than identifying the brakes by disc size alone. When selecting pads or servicing the calipers, use the exact GT3 specification for BRK.200645; a familiar rotor diameter does not establish compatibility.

Floating Two-Piece Rotors

Pro-System’s two-piece floating rotor design separates the iron friction ring from the aluminum mounting hat. Under repeated hard braking, the ring heats and expands much faster than the hub area. The floating attachment accommodates that growth instead of forcing the friction ring and hat to behave as a single rigid casting. It also provides a serviceable assembly: a worn ring can be replaced while a sound hat is retained.

Ventilation and Friction Surface

Braking converts the car’s kinetic energy into heat. The rotor must absorb that energy during the stop and release it between braking zones. Pro-System’s ventilated, slotted iron rotors combine internal cooling passages with a machined friction face. The vanes move air through the disc, while the slots help keep the pad contact surface clear. Rotor diameter, thickness, pad selection and cooling airflow all contribute to the system’s operating temperature.

Pro-System Rotor Preparation

Pro-System machines its iron rotors in Mooresville, North Carolina, using a specially formulated grey cast iron chosen for thermal stability and friction performance. Dyno bedding prepares the rotor friction surfaces under controlled conditions before installation. This preparation is part of the Pro-System approach to building a brake package, alongside precision-machined hats, dedicated brackets and floating rotor hardware. Pad inclusion and compound remain specific to the ordered kit.

Hats, Brackets and Serviceability

The rotor hat connects the friction ring to the hub; the caliper bracket locates the caliper relative to that ring. Their dimensions are application-specific, even when two kits use the same caliper family or rotor diameter. Keeping the correct combination matters for alignment, pad contact and clearance. Order replacement rings, hats, brackets and mounting hardware against the complete kit part number. Rotor bobbin components are supplied as complete hardware kits.

Wheel Fitment and Installation

Check the complete caliper and rotor envelope against the wheels fitted to your car. Spoke profile, barrel shape, offset and balancing-weight placement can all affect clearance. Confirm the exact M2, M3 or M4 application and factory brake configuration before ordering.

Replacement Parts

For replacement rotor rings, pads, calipers or mounting hardware, contact Alconkits with kit BRK.200645 and the axle being serviced. We will match the replacement to your exact configuration.

Gallery images show representative Pro-System component families. Application-specific components may differ.